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AssigneeStudsvik Energiteknik AB
InventorThomas Robinson
Estimating the term…
A method and an apparatus for transmitting and receiving electromagnetically generated ultra-sound, particularly for non-destructive testing of electrically conductive material, comprising the steps of generating one or more magnetic fields by means of one or more electromagnets (1,2,3,4) and supplying to a transmitter coil (8) in said magnetic field a supersonic frequency, and scanning a receiver coil (52) in said magnetic field. For known apparatuses the signal/noise ratio of a received signal is unfavorable, especially at the testing of non-magnetic material. According to the present invention said ratio is improved in that said magnetic field is generated during a short time compared with the time between two subsequently occurring magnetic fields, and a pulse well-defined in length of supersonic frequency is supplied to the transmitter coil (8) about or at the maximum strength of the magnetic field or fields. The receiver coil (52) thereafter is scanned, but also about or at the maximum strength of the magnetic field or fields. The said pulse has a preferred length of one or two complete sinusoidally-shaped cycles, whereafter the signal is cancelled entirely. According to a preferred embodiment the said pulse is generated through a thyristor-controlled (42) discharge circuit comprising a capacitor (38) and a vacuum gap tube (37). According to a preferred embodiment there is further provided a high-pass filter (53) between the receiver coil (52) and an amplifier (54).
A method of transmitting and receiving electromagnetically generated and received pulses of ultrasound, primarily for non-destructive testing of electrically conductive material, especially steel with a temperature above the Curie-temperature, comprising the steps of generating one or more magnetic fields by one or more electromagnets (1, 2, 3, 4) where each magnetic field is generated in the form of pulses by a first pulse generator (5) and where each magnetic field pulse has a duration that is short as compared with the time interval between two successively occurring magnetic field pulses, characterized in that a tailess ultrasonic pulse of well-defined length is developed in said material by conducting an electrical current pulse through a transmitter coil (8) in one of the magnetic fields at or about the maximum magnetic field strength, that thereafter a signal resulting from the ultrasonic pulse is received at a receiver coil (52) in one of said magnetic fields, that said receiver coil is scanned also at or about maximum magnetic field strength for said signal, that said current pulse is conducted through said transmitter coil only for a time that is substantially shorter than each magnetic field pulse, and that said current pulse is generated by a second pulse generator (7) and consists of at least one or a plurality of cycles of a sinusoidal wave.
An apparatus for generating and receiving pulses of ultrasound primarily for non-destructive testing of electrically conductive material, comprising one or more electromagnets (1, 2, 3, 4) for generating a corresponding number of magnetic fields, a transmitter coil (8) located in one of said fields, a receiver coil (52) located in one of said fields, a first pulse generator (5) for supplying energy to each electromagnet in the form of time-spaced pulses each having a duration that is short as compared with the time interval between successively occurring ones of said time-spaced pulses, and a second pulse generator (7) for supplying an electrical current pulse of supersonic frequency to said transmitter coil at or about the maximum strength of each of the magnetic fields to develop a tailess ultrasonic pulse of pre-selected length in said material, said current pulse having a duration which is substantially shorter than each magnetic field and consisting of at least one or a plurality of cycles of a sinusoidal wave, said ultrasonic pulse being effective to develop a signal in said receiver coil, and means (54,55) for sensing reception of said signal by said receiver coil at or about the maximum strength of each magnetic field after the said current pulse is supplied to said transmitter coil.
Dependencies are inferred from the claim text.